The Nebuale award is an award given to the best alcoholic beverages and such. In the year prior to Roger Wilco's shore leave on Polysorbate LX, the award was given to Ursula K. LeGuiness Stout, a perenially popular refreshment.
"Nebuale" is a combination of the words "Nebulae" and "Ale". It is a play on the Nebula Award, an award given to fantasy/sci-fi authors. In 1994 (the year before SQ6 was released) Ursula K. LeGuin won the Nebula for the short story "Solitude", one of four such awards in her career.